1. Field of the Invention
The present invention relates to a received-signal combining method and system, and, in particular, to a received-signal combining method and system for receiving signals provided from a radio-transmitting station by a plurality of radio-receiving stations, and generating a reception signal based on the signals provided by the plurality of radio-receiving stations.
Further, the present invention relates to a radio-receiving station and receiving station used in such a received-signal generating method.
2. Description of the Related Art
In the related art, for example, a radio-transmitting system such as a mobile communication system rendering uplink site diversity includes, as shown in FIG. 1, a plurality of radio-receiving stations 2 (for example, base stations) are connected to a receiving station 3 (for example, control station), and, a radio-transmitting station 1 (for exmaple, a mobile set) is connected with the plurality of radio-receiving stations 2 via radio transmission paths, and renders communication therewith. In such a radio-transmitting system, each radio-receiving station 2 receives, from the radio-transmitting station 1, radio waves transmitted after having undergone respective processes such as error-correction coding, modulation and so forth, and, then, demodulates it and renders error-correction decoding thereon, and, then, transmits the result thereof to the receiving station 3. Then, the receiving station 3 generates a reception signal by rendering selection combining on the error-correction decoding results provided from the respective radio-receiving stations 2.
By employing such a radio-transmitting system, it is possible to reduce degradation in quality of the reception signal obtained by the receiving station 3 to the utmost, even when transmission characteristics of the radio transmission paths between the radio-transmitting station 1 and radio receiving stations 2 are degraded due to shadowing or the like.
Further, in such a radio-transmitting system, it can be considered to transmit the demodulated output of each radio-receiving station 2 without performing error-correction decoding thereon to the receiving station 3, and, the receiving station 3, after performing maximum ratio combining on the thus-obtained signals, performs error-correction decoding. By such a method, it is possible to further improve the quality of the reception signal.
However, in this method, because the demodulated outputs of the radio-receiving stations 2 are transmitted between the radio-receiving stations 2 and the receiving station 3, the amount of information transmitted therebetween is large. Thereby, it is necessary to set a large transmission capacity of the transmission paths (wired or radio) therebetween.